Iranian officials have instructed residents of Isfahan to leave the city, renewing concerns that a nearby nuclear site could be leaking radioactive material.

An edict issued Wednesday by Iranian authorities orders Isfahan’s one-and-a-half million people to leave the city “because pollution has now reached emergency levels,” the BBC reported.

However, outside observers suspect that the evacuation order may corroborate previous reports indicating that a uranium enrichment facility near Isfahan had been leaking radioactive material.

Tehran went to great lengths in December to deny these reports, tellingstate-run media outlets that “the rumors about leaking and contamination at Isfahan’s [Uranium Conversion Facility] are not true at all.”